Disclosed herein are black phase change inks and methods for making same. In one embodiment the black phase change ink composition can comprise (1) a low polarity ink carrier comprising (A) an ester-terminated polyamide, (B) a Guerbet alcohol or a Guerbet alcohol mixture including at least one linear alcohol, and (C) a low polarity wax, and (2) a black colorant. The ink carrier can also include a dispersant. The ink can be resistant to substantial aggregation and settling of the black colorant at the standby-mode printer temperature for the ink and up to about the jetting temperature of the ink. In one embodiment, the phase change ink can be a low energy black phase change ink.
Another embodiment is directed to a method which comprises (a) incorporating into an ink jet printing apparatus the above-described phase change ink composition; (b) melting the ink; (c) causing droplets of the melted ink to be ejected in an image wise pattern onto an intermediate transfer member; and (d) transferring the ink in the image wise pattern from the intermediate transfer member to a final recording substrate.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the printhead operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking, industrial marking, and labeling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
U.S. Pat. No. 5,783,657, U.S. Pat. No. 5,998,570 and WO 98/17704, (Pavlin et al), the disclosures of each of which are totally incorporated herein by reference, disclose a low molecular weight, ester-terminated polyamide that may be blended with a liquid hydrocarbon to form a transparent composition having gel consistency. The ester-terminated polyamide is prepared by reacting “x” equivalents of dicarboxylic acid wherein at least 50 percent of those equivalents are from polymerized fatty acid, “y” equivalents of diamine such as ethylene diamine, and “z” equivalents of monoalcohol having at least 4 carbon atoms. The stoichiometry of the reaction mixture is such that 0.9≦{x/(y+z)}≦1.1 and 0.1≦{z/(y+z)}≦0.7. The reactants are heated until they reach reaction equilibrium.
U.S. Pat. No. 6,111,055 (Berger, et al), the disclosure of which is totally incorporated herein by reference, discloses an ester terminated dimer acid-based polyamide which is blended with a solvent to form a gel. The solvent may be flammable, and a wick may be added to the resulting gel to form a candle. The said ester terminated dime racid-based polyamide is prepared by thermal condensation of a diacid, a diamine and a monoalcohol.
Compositions suitable for use as phase change ink carrier compositions are known and are described in U.S. patent application Ser. No. 10/881,047, now U.S. Pat. No. 6,989,052 the disclosure of which is totally incorporated herein by reference.
A need remains for improved phase change inks, and more specifically, low energy solid inks which permit phase change ink jet printers to perform at more moderate operating conditions than with conventional phase change inks. For example, a need exists for phase change inks which can be jetted at temperature lower than conventional jetting temperature as described below. However, black colorants commonly used in phase change inks can interfere with the gelling process at these lower than conventional operating conditions and might therefore present difficulties for black ink compositions during low energy operation. While these black inks give excellent print quality and performance at higher energy levels, there is still a need for black inks that minimize penetration of the colorant in the paper during the transfer/fusing stage of the printing process for minimum show through after fusing at low energy conditions. Additionally, there is a need to eliminate problems associated with black dye diffusion at reduced operating temperatures. Furthermore, there is a need for black phase change inks that generate prints with good performance in automatic document feeders. Additionally, there is a need for stable (no settling of pigment) black dispersions. Thus, a need exists for a black phase change ink which is resistant to aggregation and settling of the black pigment particles, and more particularly, in a phase change ink jet printer, when the standby-mode printer temperature for the ink is at less than the temperature at which the gel transition for an ink is observed. Additionally, a need remains for black phase change inks that print successfully on paper and transparency stock. Moreover, there is a need for black phase change inks that generate prints with good performance in automatic document feeders.